HashMap存储自定义类型键值和LinkedHashMap集合

HashMap存储自定义类型键值

1、当给HashMap中存放自定义对象时，如果自定义对象是键存在，保证键唯一，必须复写对象的hashCode和equals方法。

2、如果要保证map中存放的key和取出的顺序一致，可使用LinkedHashMap集合来存放

public class Person {
    private String name;
    private int age;
    public Person(String name, int age) {
        super();
        //有参构造
        this.name = name;
        this.age = age;
    }//无参构造
    public Person() {
        super();
    }
    //get  set
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    //toString方法
    public String toString() {
        return "Person [name=" + name + ", age=" + age + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    //哈西和equals
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Person other = (Person) obj;
        if (age != other.age)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
}

public class Demo03 {
    public static void main(String[] args) {
        Map<Person,String> map=new HashMap<Person,String>();
        map.put(new Person("胸大",22),"java0322班");
        map.put(new Person("胸二",20), "java0222班");
        map.put(new Person("胸二",20), "java0262班");
        //遍历
        //1.获取装有所有key的Set集合
        Set<Person> set=map.keySet();
        //2.遍历set集合取到每一个key
        for(Person key:set){
            System.out.println(key+"..."+map.get(key));
        }
    }
}

LinkedHashMap

public class Demo04 {
    public static void main(String[] args) {
        Map<String,Person> map=new LinkedHashMap<String,Person>();
        //添加数据
        map.put("java0322",new Person("胸三",33));
        map.put("java0222",new Person("胸大",33));
        map.put("java0611",new Person("胸三",33));
        //遍历(entrySet迭代器)
    //1.获取所有结婚证存在的集合
        Set<Map.Entry<String,Person>> set=map.entrySet();
        //2.获取迭代器对象
        Iterator<Map.Entry<String,Person>> it=set.iterator();
        //3.循环判断下个元素是否有值
        while(it.hasNext()){
            //4.获取每一个结婚证对象
            Map.Entry<String, Person> entry=it.next();
            //5.从结婚证对象中获取key
            String key=entry.getKey();
            //6.从结婚证对象中获取value
            Person value=entry.getValue();
            System.out.println(key+"..."+value);
        }
    }
}